MSA-like growth factors are produced by a human fibrosarcoma cell line and released into their tissue culture media. A fibrosarcoma specific growth hormone has been purified to apparent homogeneity by gel permeation, ion exchange and affinity chromatography. This peptide was shown to bind and to require the MSA receptor in order to function as a growth factor. The binding and elution from its own binding protein yielded a 1500-fold purification over the material in the tissue culture supernatant.